Non-sticky erasable media with overcoat

Abstract

Exemplary embodiments provide an erasable medium having an overcoat layer on a photochromic layer to provide a non-adhesive surface for the erasable medium when exposed to high temperatures, wherein the overcoat layer can include a latex or a mixture of a latex and a wax.

What is claimed is: 
     
       1. An erasable print medium comprising:
 a flexible substrate, wherein the flexible substrate is one of a paper substrate, an opaque plastic substrate, a metal substrate, and a wood substrate; 
 a first photochromic layer disposed over at least one surface of the flexible substrate, wherein the first photochromic layer is configured to exhibit a reversible color change from a first form to a second form when exposed to radiation and from the second form to the first form when heated; and 
 an overcoat layer disposed over the first photochromic layer, wherein the overcoat layer comprises a mixture of a latex and a wax, the latex comprising a polymer selected from the group consisting of acrylate, styrene acrylate, rubber, polyester, sulfonated polyester, and a mixture thereof and the wax being in a form of fine particles having a particle size of 500 nm or less. 
 
     
     
       2. The erasable print medium of  claim 1 , wherein the first photochromic layer is disposed on one side of the flexible substrate and a second photochromic layer is disposed on an opposite side of the flexible substrate, wherein the overcoat layer is disposed over each of the first photochromic layer and the second photochromic layer. 
     
     
       3. The erasable print medium of  claim 1 , wherein the erasable print medium is non-adhesive to a printing component or to a surface layer of a second print medium at a temperature of about 40° C. or greater. 
     
     
       4. The erasable print medium of  claim 1 , wherein the overcoat layer has a document offset SIR (standard image reference) mark with a surface layer of a second print medium, wherein the offset SIR mark is at least about 4.0 after stacking the overcoat layer on the surface layer of the second print medium at a temperature of about 50° C. or greater for more than about 24 hours under a pressure ranging from about 60 g/cm 2  to about 100 g/cm 2 . 
     
     
       5. The erasable print medium of  claim 1 , wherein the erasable medium is erasable for at least about 100 times, wherein each of the at least about 100 times comprises subjecting the erasable print medium to a temperature of about 150° C. and a speed of about 5 ppm. 
     
     
       6. The erasable print medium of  claim 1 , wherein the overcoat layer has a thickness ranging from about 0.1 microns to about 30 microns. 
     
     
       7. The erasable print medium of  claim 1 , wherein the latex is in a form of a particle having an average particle size ranging from about 50 nm to about 200 nm. 
     
     
       8. The erasable print medium of  claim 1 , wherein the wax is a material selected from the group consisting of polyethylene, polypropylene, polyethylene copolymer, Fischer-Tropsch waxes, oxidized waxes, plant based waxes, animal based waxes, petroleum based waxes, ester waxes obtained from higher fatty acid and higher alcohols, ester waxes obtained from higher fatty acid and monovalent or multivalent lower alcohol, ester waxes obtained from higher fatty acid and multivalent alcohol multimers, sorbitan higher fatty acid ester waxes, cholesterol higher fatty acid ester waxes, functionalized waxes comprising amine, amide, fluorinated or chlorinated waxes, mixed fluorinated amide waxes, imides, esters, quaternary amines, carboxylic acids or acrylic functionalized waxes, and a combination thereof. 
     
     
       9. The erasable print medium of  claim 1 , wherein wax is present in an amount ranging from about 10% to about 20% by weight of the latex present in the overcoat layer. 
     
     
       10. The erasable print medium of  claim 1 , wherein the first photochromic layer comprises a photochromic moiety selected from the group consisting of spiropyrans, spirooxazines, chromenes, spirodihydroindolizines, spiroperimidines, azobenzenes, thioindigos, thiospiropyrans, benzos, stilbenes, bisimidazols, quinines, perimidinespirocyclohexadienones, viologens, fulgides, fulgimides, diarylethenes, hydrazines, anils, aryl thiosulfonates, and combinations thereof. 
     
     
       11. The erasable print medium of  claim 1 , wherein the first photochromic layer comprises a photochromic composite comprising:
 a photochromic polymer comprising a photochromic moiety covalently bound to a backbone portion, wherein the photochromic polymer has a glass transition temperature ranging from about 30° C. to about 150° C.; and 
 a polymer binder, wherein the polymer binder and the backbone portion of the photochromic polymer each comprises at least one similar functional group. 
 
     
     
       12. The erasable print medium of  claim 1 , wherein the first photochromic layer with the overcoat layer disposed thereover converts from a colorless state to a colored state using a radiant energy having a wavelength from about 200 nm to about 475 nm and at a temperature ranging from about 30° C. to about 150° C.; and reverts from a colored state to a colorless state at a temperature of about 70° C. or higher. 
     
     
       13. The erasable print medium of  claim 1 , wherein the first photochromic layer with the overcoat layer disposed thereover can be exposed to imaging radiation passing through the overcoat layer so as to convert the first photochromic layer from a colorless state to a colored state using a radiant energy having a wavelength from about 200 nm to about 475 nm and at a temperature ranging from about 30° C. to about 150° C. 
     
     
       14. An erasable print medium comprising:
 a flexible substrate, wherein the flexible substrate is one of a paper substrate, an opaque plastic substrate, a metal substrate, and a wood substrate; 
 a first photochromic layer disposed over at least one surface of the flexible substrate, wherein the photochromic layer is configured to exhibit a reversible color change from a first form to a second form when exposed to radiation and from the second form to the first form when heated; and 
 an overcoat layer disposed over the first photochromic layer, wherein the overcoat layer comprises a mixture of a latex and a wax, the wax is a fluorinated wax, the overcoat layer is non-adhesive at a temperature of more than about 50° C. to at least one of a printing component or a surface layer of a second print medium and the wax being in a form of fine particles having a particle size of 500 nm or less. 
 
     
     
       15. The erasable print medium of  claim 14 , wherein the first photochromic layer is disposed on one side of the flexible substrate and a second photochromic layer is disposed on an opposite side of the flexible substrate, wherein the overcoat layer is disposed over each of the first photochromic layer and the second photochromic layer. 
     
     
       16. The erasable print medium of  claim 14 , wherein the first photochromic layer with the overcoat layer disposed thereover retains an image for at least about 24 hours, and wherein the image has an initial optical density difference (ΔOD) with a background area of about 0.75 or greater. 
     
     
       17. The erasable print medium of  claim 16 , wherein the image has a ΔOD of at least about 40% of the initial ΔOD after 3 days from an initial imaging. 
     
     
       18. The erasable print medium of  claim 14 , wherein the first photochromic layer with the overcoat layer disposed thereover can be exposed to imaging radiation passing through the overcoat layer so as to convert the first photochromic layer from a colorless state to a colored state using a radiant energy having a wavelength from about 200 nm to about 475 nm and at a temperature ranging from about 30° C. to about 150° C. 
     
     
       19. An erasable print medium comprising:
 a flexible substrate, wherein the flexible substrate is one of a paper substrate, an opaque plastic substrate, a metal substrate, and a wood substrate; 
 a first photochromic layer disposed over at least one surface of the flexible substrate, wherein the first photochromic layer is configured to exhibit a reversible color change from a first form to a second form when exposed to radiation and from the second form to the first form when heated; and 
 a clear overcoat layer disposed over the first photochromic layer, wherein the clear overcoat layer comprises a mixture of a latex and a wax, the wax being present in an amount ranging from about 10% to about 20% by weight of the latex present in the clear overcoat layer, the wax being in a form of fine particles having a particle size ranging from about 50 nm to about 300 nm, 
 wherein the latex comprises a polymer selected from the group consisting of acrylate, styrene acrylate, rubber, polyester, sulfonated polyester, and a mixture thereof 
 wherein the wax is a material selected from the group consisting of polyethylene, polypropylene, polyethylene copolymer, Fischer-Tropsch waxes, oxidized waxes, plant based waxes, animal based waxes, petroleum based waxes, ester waxes obtained from higher fatty acid and higher alcohols, ester waxes obtained from higher fatty acid and monovalent or multivalent lower alcohol, ester waxes obtained from higher fatty acid and multivalent alcohol multimers, sorbitan higher fatty acid ester waxes, cholesterol higher fatty acid ester waxes, functionalized waxes comprising amine, amide, fluorinated or chlorinated waxes, mixed fluorinated amide waxes, imides, esters, quaternary amines, carboxylic acids or acrylic functionalized waxes, and a combination thereof. 
 
     
     
       20. The erasable print medium of  claim 19 , wherein the latex is a styrenated acrylic copolymer latex.